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At the same time, certain physical qualities of this latter 
are modified, for the quarrymen who are accustomed to work 
slate, quartzose, or other siliceous rocks find a great difference 
in. the facility of their task between those substances still 
containing their “ quarrywater,” or those deprived of this water 
by exposure to the air. Already had the Romans turned to 
account the porosity of onyx, in order to cause certain liquids 
to penetrate and heighten the colour of these agates intended 
for their cameos. Under this latent form of intimate impreg- 
nation, and however feeble may be the relative proportion, 
water is incorporated even in the quartz of granites or granu- 
lites, &c. It is a well-known fact that at the present day, in 
mountain regions, such as Chamonix in the Haute Savoie, where 
strangers much resort, flint stones of light colour are prepared 
for sale, by being boiled in a blue solution, and sold to the 
unwary as Lapis Lazuli. 
The property then of granites to absorb and retain water 
within the pores of their compound minerals, is unquestionable. 
From the character of porosity in rocks, the line of inquiry 
would as regards the presence of water in the mineral contents 
of the granitic rocks, lead to a passing reference to the water 
existing in chemical combination, as for examples in the hydrous 
silicates, a class or group containing numerous minerals, a large 
and important number of these being magnesian, like Steatite 
and Serpentine, or again, like Muscovite and Damourite, the 
mica so often present in granitic rocks; on the other hand quartz 
is anhydrous, yet in some of its conditions, colloidal or quasi 
colloidal, as in Opal which contains from 3 to 13 per cent. of 
water, and is a solidified gelatinous silicate; it has water in its 
intimate structure chemically combined. The test for the water 
in hydrated minerals is generally simple, but should be carefully 
conducted; the mineral has only to be submitted in a small 
glass flask, or ‘ Berzelius-tube,’ to a sufficient heat of say 100 
to 120 to determine the conversion of the water into vapour, 
which condenses on cooling upon the surface. With this bare 
glance at the water in physical and chemical combination, 
attention may properly be bestowed upon the water occluded or 
